use elegant check for valid ip addresses (#372)

Also works for IPv6 addresses

src/conf.c

@@ -45,30 +45,6 @@
 #include "auth.h"
 #include "util.h"
 
-int validateIP4Dotted(const char *ip4addr)
-{
-	if (strlen(ip4addr) < 7 || strlen(ip4addr) > 15) {
-		return 0;
-	}
-
-	char tail[16];
-	tail[0] = 0;
-	int i = 0;
-	unsigned int d[4];
-	int c = sscanf(ip4addr, "%3u.%3u.%3u.%3u%s", &d[0], &d[1], &d[2], &d[3], tail);
-
-	if (c != 4 || tail[0]) {
-		return 0;
-	}
-
-	for (i = 0; i < 4; i++) {
-		if (d[i] > 255) {
-			return 0;
-		}
-	}
-	return 1;
-}
-
 
 /** @internal
  * Holds the current configuration of the gateway */
@@ -989,7 +965,7 @@ config_read(const char *filename)
 	fclose(fd);
 
 	if (config.fas_remoteip) {
-		if (validateIP4Dotted(config.fas_remoteip) == 1) {
+		if (is_addr(config.fas_remoteip) == 1) {
 			debug(LOG_INFO, "fasremoteip - %s - is a valid IPv4 address...", config.fas_remoteip);
 		} else {
 			debug(LOG_ERR, "fasremoteip - %s - is NOT a valid IPv4 address format...", config.fas_remoteip);

src/util.c

@@ -373,6 +373,14 @@ get_uptime_string(char buf[64])
 	return format_duration(started_time, time(NULL), buf);
 }
 
+int is_addr(const char* addr) {
+	struct sockaddr_in sa;
+	struct sockaddr_in6 sa6;
+
+	return (inet_pton(AF_INET, addr, &sa.sin_addr) == 1) ||
+		(inet_pton(AF_INET6, addr, &sa6.sin6_addr) == 1);
+}
+
 void
 ndsctl_status(FILE *fp)
 {

src/util.h

@@ -59,6 +59,9 @@ int is_auth_online();
 /* @brief Format a time_t value to 'Fri Jul 27 18:52:22 2018' */
 char *format_time(time_t time, char buf[64]);
 
+/* @brief Check if the address is a valid IPv4 or IPv6 address */
+int is_addr(const char* addr);
+
 /*
  * @brief Mallocs and returns nodogsplash uptime string
  */